A broadband wireless access system defines protocols between a medium access control (MAC) layer and a physical (PHY) layer for setting up a point-to-multipoint connection between a base station and a terminal. FIG. 1 illustrates a hierarchical protocol structure of a broadband wireless access system.
The physical layer of a broadband wireless access system may be broadly specified into a single carrier type and a multiple carrier type. An orthogonal frequency division multiplexing (OFDM) has mainly been used as the multiple carrier type and an orthogonal frequency division multiple access (OFDMA) in which communication resources can be allocated in a unit of a subchannel grouped by a part of carriers has been used as an access method.
Reed-Solomon (RS) code, convolution code or block turbo code can be selectively used for forward error correction (FEC) and BPSK, QPSK, 16-QAM or 64-QAM be used as a modulation scheme in a broadband wireless access system. An adaptive modulation/coding (AMC) scheme with which a modulation mode and code rate is dynamically selected according to channel state can also be used. Received signal strength indication (RSSI), carrier to interference and noise ratio (CINR) or bit error rate (BER), etc may be used in measuring channel quality for the AMC.
Active carriers are divided into a plurality of groups and each group is transmitted to a receiving side and each group is called a subchannel. Carriers belong to a subchannel can be adjacent each other or be separated with a same interval. Multiple access in a unit of a subchannel may increase complexity in implementation, but can increase frequency diversity gain and gain arising from power concentration, and can efficiently perform forward link power control.
Slots allocated to each user can be defined by 2-dimensional data region which is group of consecutive subchannels allocated by bursts. One data region in an OFDMA can be represented by a rectangular form determined with a time coordinate and a subchannel coordinate. The data region can be allocated to a user for uplink data transmission or can be used for transmitting data to a user in a forward link. The number of OFDM symbols in a time domain and the number of consecutive subchannels starting from a point separated a specific offset from a reference point in a frequency domain for defining such a data region in a 2-dimensional space.
MAC data is divided according to a FEC block size and each FEC block is expanded to occupy three OFDM symbols in a time axis of each subchannel. When the end of the data region is reached while continuing mapping in order with increasing the number of subchannel with respect to each FEC block, mapping is continued in a same manner from an OFDM symbol having a following number. FIG. 2 illustrates a procedure of mapping FEC blocks to OFDMA subchannels and OFDMA symbols.
FIG. 3 illustrates structure of a data frame in a physical channel in an OFDMA broadband wireless access system. A downlink sub-frame begins with a preamble used for synchronization and equalization. Structure of the entire frame is defined by broadcasting-based downlink DL-MAP messages and uplink UL-MAP messages defining locations and uses of bursts allocated to the downlink and uplink.
The DL-MAP and UL-MAP messages define the uses of data bursts allocated to the downlink and the uplink, respectively in a bust mode physical layer. Information elements (IEs) constituting a DL-MAP message divide downlink traffic duration by a downlink interval usage code (DIUC), a connection ID (CID), and location information of the bursts (subchannel offset, symbol offset, a number of subchannel or symbol, etc). Meanwhile, an uplink interval usage code (UIUC) defines a use of each information element constituting a UL-MAP message and ‘duration’ defines the location of the corresponding duration per each CID. In other words, the use of each duration is defined by the UIUC used in the UL-MAP and each duration begins from a point separated ‘duration’ defined in the UL-MAP IE from the start point of the former IE.
A DCD message and a UCD message include a modulation type, a FEC code type, etc which are parameters associated with the physical layer applied to burst duration allocated to the downlink and uplink, respectively. The DCD and UCD messages further include parameters necessary according to various FEC code types (e.g. K and R value of the RS code). Such parameters are given by burst profiles stipulated for each UIUC and DIUC in the UCD and DCD messages, respectively.
The MAC layer in the broadband wireless access system is basically based on the DOCSIS standard which is a cable modem standard of MCNS consortium. Core features of the MAC layer such as MAC management method and resource allocation method, etc are similar with those of the DOCSIS standard, except security guarantee according to characteristics of a wireless system, support for various type of modulation schemes, and partial addition and amendment.
A service-specific convergence sublayer (CS) is a layer above a MAC CPS (common part sublayer) and performs functions of reception, classification, and process of protocol data units (PDUs) received from an upper layer, and transfer of CS PDU to an appropriate MAC SAP, and reception of CS PDUs from a peer entity. Further, the CS classifies upper layer PDUs for each connection and optionally provides the functions of compressing payload header information or restoring compressed header information.
The MAC CPS performs mapping of each packet to an appropriate connection-based service flow during packet transmission between a terminal and a base station and provides different levels of quality of service (QoS) according to the connection-based service flow. The formats of MAC PDUs defined by the MAC CPS are described below.
FIG. 4A illustrates a format of a MAC PDU. The MAC PDU can be classified into a MAC management PDU and a user data MAC PDU. The MAC management PDU comprises a payload part including MAC management messages pre-determined for actions of the MAC layer and a header part located before the payload part. A band request PDU is a special type of MAC management PDU including a header called a band request header without the payload part. The band request header is made to be transmitted through contention-based uplink band so that it may be used for requesting uplink band by a terminal which has not been allocated with uplink band from a base station. FIG. 4B illustrates an example of the band request header.
A packet PDU corresponding user data is mapped to the payload part of a MAC SDU and a MAC header and cyclic redundancy check (CRC) bits (optional) are attached to the packet PDU to be a MAC PDU. FIG. 4C illustrates an example of an uplink burst including a plurality of consecutive MAC PDUs. Each MAC PDU is identified by an original connection ID (CID) and MAC management messages, band request PDU, etc as well as user PDU can be included in a same burst.
A MAC management message comprises a field representing a type of the management message and a payload part. A DCD, UCD, UL-MAP, and DL-MAP are representative examples of the management message, as described above, defining parameters of a frame structure, band allocation, and physical layer.
A scheduling service is adopted for increasing efficiency of a polling/transmission admission procedure. A base station may forecast a permissible scope of delay and throughput of uplink traffic by showing explicitly a scheduling service and a quality of service (QoS) parameter related to the scheduling service, thereby the polling and transmission permission is provided in an appropriate time. The polling is a procedure that the base station allocates bandwidth to each terminal in response to the request of bandwidth allocation by the each terminal. The types of the scheduling service provided by the current specification are specified into an unsolicited grant service (UGS), real-time polling service (rtPS), non-real-time polling service (nrtPS), and best effort (BE). Additional band allocation request is possible through a piggybacking or polling, etc and with respect to other types of scheduling services other than the UGS bandwidth allocated for a connection can be re-distributed for another connection within a scope of total bandwidth allocated per a terminal.
An automatic repeat request (ARQ) protocol is selectively supported in the broadband wireless access system. A MAC SDU is divided into at least one ARQ fragment to be transmitted in a form of sliding window in a selective repeat ARQ scheme and error detection is performed per fragment with cyclic redundancy check (CRC). Parameters like ARQ_WINDOW_SIZE, ARQ_FRAGMENT_LIFETIME, ARQ_RETRY_TIMEOUT, etc are provided for the sliding window protocol and ACK or NACK is noticed through an ARQ-Feedback message. Types of the ACK can be classified into ‘Selective ACK’, ‘Cumulative ACK’, and ‘Cumulative with Selective ACK’. One of the three types of ARQ scheme can be defined and used dynamically for a connection according to a mutual agreement between a transmitting side and a receiving side. The ACK can be transmitted to the transmitting side in a form of a MAC message independently or in a piggyback type. Receiving an ARQ fragment, the receiving side transmits an ACK feedback information element (IE) or data piggybacked with ACK/NACK as a reply to the transmitting side.
Table 1 and Table 2 represent a format of an ARQ feedback message and an ARQ feedback IE included in the ARQ feedback message, respectively. At least one ACK MAP is included in the ACK feedback IE for indicating the type of ACK and ARQ fragments received without error. The three types of ACK can be identified by the format constituting ACK MAP with respect to ARQ fragments with which errors occur.
TABLE 1SizeSyntax(bits)NotesARQ_Feedback_Message_Format( ){ Management Message Type = 338 ARQ_Feedback_Payloadvariable}
TABLE 2SizeSyntax(bits)NotesARQ_feedback_IE(LAST){variable CID16The ID of the connection beingreferenced. LAST10 = More ARQ feedback IE in thelist1 = Last ARQ feedback IE in thelist. ACK Type20x0 = Selective ACK entry0x1 = Cumulative ACK entry0x2 = Cumulative withSelective ACK entry0x3 = Cumulative ACK withBlock Sequence ACK entry BSN11 Number of ACK Maps2If ACK Type==01, the field isreserved and set to 00.Otherwise the field indicates thenumber of ACK maps: 0x0=1,0x1=2, 0x2=3, 0x3=4 if(ACK Type!=01){  for(i=0; i<Numberof ACK Maps+1; i++){  if(ACK Type !=3){   Selective ACK16Map  }  else{Start of Block Sequence ACK Mapdefinition (16 bits)  Sequence Format1Number of block sequencesassociated with descriptor. 0:2block sequences 1: 3blocksequences  if(SequenceFormat=0){   Sequence ACK Map2   Sequence 16Length   Sequence 26Length   Reserved1  }  else{   Sequence ACK Map3   Sequence 14Length   Sequence 24Length   Sequence 34Length  }   }End of Block Sequence ACK Mapdefinition  } }}
FIGS. 5A-5C illustrate examples of a method of configuring the ACK MAP in accordance with each ACK type. In the type of ‘Selective ACK’ whether error occurs for each and every ARQ fragment is indicated by ‘0’ or ‘1’ to be noticed. In the type of ‘Cumulative ACK’ a frame sequence number (MSN) of the last ARQ fragment received without error is noticed. Meanwhile, ‘Cumulative with Selective ACK’ is a combination type of ‘Selective ACK’ and ‘Cumulative ACK’.
The broadband wireless access system supports an idle mode to reduce power consumption of a terminal. In the case of the idle mode, although the terminal which has not yet been registered in a specific base station (BS) does not perform handover from one base station (BS) to other BS in a paging zone comprising a plurality of BS areas, the terminal receives a predetermined paging message (MOB-PAG-ADV), such that it can periodically recognize the presence or absence of downlink traffic toward the terminal itself, resulting in minimum power consumption of the MSS.
A paging-group-action message transmitted on wire between base stations may be used for configuring a paging zone. Table 3 is an example of a format of the paging-group-action message.
TABLE 3SizeField(bits)NotesPaging-group-actionMessage Format( ) { Message Type8 Sender BS-ID48Base station uniqueidentifier (Same number asthat broadcasted on theDL-MAP message) Target BS-ID48Base station uniqueidentifier (Same number asthat broadcasted on theDL-MAP message) Time Stamp32Number of millisecondssince midnight GMT (set to0xffffffff to ignore) Action40 - Assign target BS topaging groups1 - Remove target BS frompaging groups2 - Query (which paginggroups target BS belongsto?)3 - Information (paginggroups sender BS belongs to) Num Records4Number of paging-group-IDrecords For (j=0; j<NumRecords; j++) {  Paging-group-ID16Paging-group-ID  PAGING_CYCLE16Cycle in which the pagingmessage is transmit-tedwithin the paging group  PAGING OFFSET8MSS PAGING OFFSET parameter} Security fieldTBDA means to authenticate thismessage CRC field32IEEE CRC-32}
The Paging-group-action message is exchanged between a paging controller and a base station or between base stations. The Paging-group-action message may be used with the following four purposes according to action codes.
First, a target BS receiving the Paging-group-action message can be included in a specific paging group (Action=0). Second, the target BS can be deleted from a paging group (Action=1). Third, the target BS can be asked whether to belong to a paging group (Action=2). Fourth, the target BS can be informed to which paging group a sender BS belongs (Action=3).
Since a base station may belong to a plurality of paging zones, information associated with a plurality of paging groups can be included in the Paging-group-action message. Base stations can obtain a paging cycle and paging offset used in each paging zone through the Paging-group-action message. The Paging-group-action message enables base stations to be dynamically allocated in paging groups.
FIG. 6 illustrates an example of configuring a paging zone to which a plurality of base stations supporting idle mode belong.
A terminal uses a de-registration request (DREG-REQ) message for going into an idle mode state. Table 4 represents an example of a format of the DREG-REQ message.
TABLE 4SyntaxSizeNotesDREG-REQ   messageformat( ) {Management message8 bitstype = 49De-registration_Request_Code8 bits0x00 = MSS de-registrationrequest from BS and network0x01 = request for MSSde-registration fromServing BS and initiation ofMSS Idle Mode0x02-0xFF = ReservedTLV encoded parametersvariable}
Table 5 describes ‘TLV encoded parameters’ of the DREG-REQ message in detail.
TABLE 5NameTypeLengthValuePaging2Requested cycle in which the pagingCyclemessage is transmitted within theRequestpaging group.Idle Mode1MSS request for Paging Controller Retainretention of network re-entryInforma-related MAC managementtionmessage MSS service and operationalinformation to expedite future NetworkRe-entry from Idle Mode. For each Bitlocation, a value of ‘0’ indicates theinformation associated with the specifiedMAC management message is not requestedto be retained and managed, a value of ‘1’indicates the information is requestedto be retained and managed.Bit #0: Retain MSS service and operationalinformation associated withBit #1: Retain MSS service and messagesBit #2: Retain MSS service and operationalSBC-REQ/RSP MAC management messagesinformation associated withREG-REQ/RSP MAC managementBit #3: Retain MSS service and operationalinformation associated with NetworkAddress Bit #4: Retain MSS service andoperational information associated withTime of Day AcquisitionBit #5: Retain MSS service and operationalinformation associated with TFTP MACmanagement messagesBit operational information associated withPKM-REQ/RSP MAC management #6:Retain MSS service and operationalinformation associated with Full service(MAC state machines, CS classifierinformation, etc . . . )
A terminal requests to shift its state into the idle mode by transmitting to a base station the DREG-REG message having ‘0x01’ as the ‘De-registration Request Code of the DREG-REG message. The terminal may deliver a preferable paging cycle and management resource information desired by the base station to be maintained after transition into the idle mode.
After receiving the DREG-REQ message, the base station may respond to it through a de-registration command (DREG_CMD) message. Table 6 is an example of a format of the DREG_CMD message.
TABLE 6SyntaxSizeNotesDREG-CMD_Message_Format( ) {Management Message Type = 298 bitsAction Code8 bitsTLV encoded parametersvariable}
The base station may send the terminal a reply to the request of the state transition with ‘Action Code’ of the DREG_CMD message. For example, the Action Code ‘0x05’ allows the state transition, ‘0x06’ makes the terminal re-request the state transition after a specific time period, and ‘0x07’ makes the terminal not request until the base station transmits the DREG_CMD message.
Table 7 describes the Action code of the DREG_CMD message and the meaning thereof in detail.
TABLE 7ActionCodeAction0x00MSS shall immediately terminate servicewith the BS and attempt network entry atanother BS0x01MSS shall listen to the current BS butshall not transmit until an RES-CMDmessage or DREG_CMD with Action Code 0x00is received.0x02MSS shall listen to the current BS butonly transmit on the Basic, PrimaryManagement, and Secondary ManagementConnections.0x03MSS shall return to normal operation andmay transmit on any of its activeconnections.0x04MSS shall terminate current NormalOperations with the BS; the BS shalltransmit this action code only inresponse to any MSS DREG-REQ0x05require MSS de-registration from ServingBS and request initiation of MSS Idle Mode0x06The MSS may retransmit the DREG-REQmessage after the time duration(REQ-duration) provided in the message0x07The MSS shall not retransmit the DREG-REQmessage and shall wait the DREG-CMDmessage0x08-0xFFReserved
The base station can transmit to the terminal a paging group ID, paging cycle, and paging offset to be maintained during the idle mode through a type length value (TLV) selectively included in the DREG_CMD message. Table 8 describes paging information included in the DREG_CMD message as a TLV parameter, management resource information of the terminal which is managed by the base station after state transition into the idle mode, and an identifier of a paging controller, etc. The information managed by the base station during the idle mode enables the terminal to perform a fast network registration and location update by omitting a procedure for obtaining the information when the terminal performs a procedure of idle mode termination, location update, or network registration.
TABLE 8NameTypeLengthValuePaging4Bits 15:0 - PAGING_CYCLE -InformationCycle in which the pagingmessage is transmitted withinthe paging groupBits 23:16 - PAGING OFFSET -Determines the frame within thecycle in which the pagingmessage is transmitted. Must besmaller than PAGING CYCLE valueBits 31:24 - Paging-group-ID -ID of the paging group the MSSis assigned toREQ-duration1Waiting value for the DREG-REQmessage retransmission(measured in frames)Paging6This is a logical networkControlleridentifier for the Serving BSIDor other network entityretaining MSS service andoperational informationand/or administering pagingactivity for the MSS while inIDLE ModeIdle Mode1Idle Mode Retain Information isRetainprovided as part of thisInformationmessage is indicative only.Network Re-entry from Idle Modeprocess requirements maychange at time of actualreentry. For each Bit location,a value of ‘0’ indicates theinformation for the associatedreentry management messagesshall not be retained andmanaged, a value of ‘1’indicates the information forthe associated re-entrymanagement message shall beretained and managedBit #0: Retain MSS service andoperational informationassociated with SBC-REQ/RSPMAC management messagesBit #1: Retain MSS service andoperational informationassociated with PKM-REQ/RSPMAC management messagesBit #2: Retain MSS service andoperational informationassociated with REG-REQ/RSPMAC management messagesBit #3: Retain MSS service andoperational informationassociated with NetworkAddressBit #4: Retain MSS service andoperational informationassociated with Time of DayBit #5: Retain MSS service andoperational informationassociated with TFTP MACmanagement messagesBit #6: Retain MSS service andoperational informationassociated with Full service(MAC state machines, CSclassifier information, etc.)
Afterwards the terminal can maintain or terminate the idle mode by receiving a paging advertisement (MOB-PAG-ADV) message at a determined paging cycle and paging offset. Table 9 is an example of the MOB-PAG-ADV message.
TABLE 9SyntaxSizeNotesMOB_PAG-ADV_Message_Format( ) {Management Message Type=628 bitsNum_Paging_Group_IDs8 bitsNumber of PagingGroup IDs in thismessageFor       (i=0;i<Num_Paging_Group_IDs;i++) {Paging Group ID8 bits}Num_MACs8 bitsNumber of MSS MACaddressesFor (j=0; j<Num_MACs; j++) {MSS MAC Address hash24 bits The hash is obtainedby computinga CRC24on the MSS 48-bitMAC address. Thepolynomial for thecalculation is0x864CFBAction Code2 bit Paging actioninstruction to MSS00 = No ActionRequired01 = Perform Rangingto establishlocation andacknowledgemessage10 = Enter Network11 = reservedReserved6 bits}TLV Encoded InformationvariableTLV specificreservedvariablePadding bits toensure octetaligned  }
Actions of a terminal in the idle mode are summarized as follows.
1) Paging Zone: A paging zone is defined as a total region covered by a plurality of base stations belonging to a paging group. Base stations belonging to a paging group have an identical paging cycle and paging offset.
2) A terminal can request state transition into an idle mode to a base station and the base station may allow the state transition into the idle mode by transferring a paging group ID, a paging cycle, and a paging offset. At this time, the terminal and the base station enable timers for location update of the terminal in the idle mode.
3) During the idle state, the terminal is able to determine whether to maintain or terminate the idle mode, or to perform the location update through paging advertisement messages broadcasted from the base station at the paging cycle.
4) When uplink traffic data to be transmitted to the base station is generated at the terminal in the idle mode, the idle mode can be terminated at any time by the terminal.
5) When downlink traffic data to be transmitted to the terminal is generated at the base station, the base station may enable the terminal to terminate the idle mode through a paging advertisement message.
6) If the terminal in the idle state has missed a paging advertisement message at the paging cycle by loosing synchronization, etc the terminal terminates the idle mode and performs a procedure for network registration.
7) When the terminal in the idle mode has moved into another paging group or needs to perform location update using the timer, the terminal performs the location update by delivering a raging request message having a paging controller identifier and a location update instruction parameter to the base station with which the terminal is connected. The location update is performed by updating invalid parameters through a network re-registration procedure as necessary. The location update can be performed swiftly by omitting procedures which can be omitted according to management resource information managed by the base station.
Table 10 is an example of a raging request message transmitted by the terminal in the idle mode and table 11 is an example of location update information in a format of TLV parameter included in the raging request message for performing the location update of the terminal.
TABLE 10SyntaxSizeNotesRNG-REQ_Message_Format( ) {Management Message Type = 48 bitsDownlink Channel ID8 bitsTLV Encoded InformationvariableTLV specific}
TABLE 11TypeLengthName(1byte)(byte)Value (Variable-length)Location81Presence of item inUpdatemessage indicates MSSRequestaction of Idle ModeLocation Update Process,regardless of valuePaging96This is a logical networkControlleridentifier for the servingIDBS or other network entityretaining MSS service andoperational informationand/or administeringpaging activity for the MSSwhile in Idle Mode
Table 12 is an example of a raging response message transmitted to the terminal by the base station after receiving the raging request message for the location update. Table 13 is an example of a location update information TLV parameter included in the raging response message.
TABLE 12SyntaxSizeNotesRNG-RSP_Message_Format( ) {Management Message Type = 58 bitsUplink Channel ID8 bitsTLV Encoded InformationvariableTLV specific}
TABLE 13TypeLengthName(1byte)(byte)Value (Variable-length)HO211For each Bit location, a valueProcessof ‘1’ indicates theOptimizationassociated re-entrymanagement messages shall berequired, a value of ‘1’indicates the re-entrymanagement message may beomitted. Regardless of the HOProcess Optimization TLVsettings, the Target BS maysend unsolicited SBC-RSPand/or REG-RSP managementmessages Bit #0: OmitSBC-REQ/RSP managementmessages during currentre-entry processing Bit #1:Omit PKM-REQ/RSP managementmessage during currentre-entry processing Bit #2:Omit REG-REQ/RSP managementduring current re-entryprocessing Bit #3: OmitNetwork Address Acquisitionmanagement messages duringcurrent reentry processingBit #4: Omit Time of DayAcquisition managementmessages during currentre-entry processing Bit #5:Omit TFTP managementmessages during cur-rentre-entry processing Bit #6:Full service and operationalstate transfer or sharingbetween Sserving BS andTarget BS (ARQ, timers,counters, MAC statemachines, etc . . . Bit #7:post-HO re-entry MSS DL datapending at Ttar-get BSLocation2310x00 = Failure of LocationUpdateUpdate. The MSS shall performResponseNetwork Re-entry from IdleMode0x01 = Success of LocationUpdate0x10, 0x11: ReservedPaging244Paging Information shallInformationonly be included if LocationUpdate Response = 0x01 and ifPaging Information haschanged Bits 15:0 -PAGING_CYCLE - Cycle in whichthe pag-ing message istransmitted within thepaging group Bits 23:16 - PAGING OFFSET - Determinesthe frame within the cycle inwhich the paging message istransmitted. Must be smallerthan PAGING CYCLE value Bits31:24 - Paging Group ID - IDof the paging group the MSSis assigned toPaging256This is a logical networkControlleridentifier for the SservingIDBS or other network entityretaining MSS service andoperational informationand/or administering pagingactivity for the MSS while inIdle Mode. Paging ControllerID shall only be included ifLocation UpdateResponse = 0x01 and if PagingController ID has changed
A multicast and broadcast service (MBS) in a broadband wireless access system is described in detail as follows.
The MBS is a point-to-multipoint service provided by a source to a plurality of receivers through a common radio channel for using the radio resources efficiently.
FIG. 7 and FIG. 8 illustrate a reference model for a MBS in a broadband wireless access system.
As depicted in FIG. 7, a system for providing an MBS comprises an MBS media server, an MBS distribution server, a plurality of base stations (BSs), and a plurality of mobile subscriber stations (MSSs). The MBS media server provides the plurality of base stations with MBS data and performs authentication and encryption key distribution to the plurality of MSSs for MBS contents. The MBS distribution server performs scheduling of the MBS data transmitted to the plurality of BSs. Alternatively, the MBS media server may perform the scheduling of the MBS data without the MBS distribution server. The BS provides the plurality of MSSs through air interface with the MBS data received through a backbone network and the MSSs receive the MBS data from the BSs.
The MBS in the broadband wireless access system has the following features.
1) Minimization of power consumption: An MSS is able to minimize power consumption during receiving MBS data notwithstanding a current mode (e.g. normal mode, sleep mode, or idle mode) of the MSS.
2) Mobility: An MSS is provided with a seamless MBS connection during moving into other BS.
3) MBS Zone: MBS data is transmitted through MBS zones which are divided by location and different MBS zones may have different MBS establishment information (e.g. MBS connection identifiers, encryption keys, service identifiers, etc)
4) Security: The MBS data is transmitted to authenticated users only. An identical encryption key for MAC PDUs can be applied to BSs belonging to a MBS zone.
FIG. 9A and FIG. 9B illustrates procedures for a MBS in broadband wireless access system.
(1) If an MSS in an idle mode wishes to receive MBS data, the MSS terminates the idle mode and goes into a normal mode.
(2) The MSS requests MBS contents lists to at least one MBS media server through a HTTP request message.
(3) The MBS media server transmits a HTTP response message in which a MBS contents list is included. The MBS contents list included in the HTTP response message may contain a name of the MBS contents, a multicast IP address, and a port number, etc.
(4) The MSS acquiring MBS information may shift into the idle mode or maintain the normal mode.
(5) After acquiring the MBS information, the MSS transmits a service generation request (DSA-REQ) message having the multicast IP address and the port number of the MBS contents to the BS. The DSA-REQ message may be transmitted from the BS to the MSS.
(6) The BS transmits a DSX-RVD message notifying the MSS of the reception of the DSA-REQ message and performs an authentication procedure for determining whether the user is appropriate to receive the MBS contents.
(7) After performing the authentication procedure, the BS provides the MSS with downlink service parameter information (e.g. a service identifier, a multicast connection identifier, a service quality parameter, a security association identifier (SAID), etc) included in the DSA-RSP message to be transmitted.
(8) The MSS transmits a key request (PKM-REQ) message to the BS for acquiring a MBS key with which encrypted MBS PDUs can be decrypted.
(9) The BS transmits a key response (PKM-RSP) message including an MBS key to the MSS.
(10) The MSS decrypts the encrypted MAC PDU received from the BS.
A MBS zone is described in detail as follows.
MBS related parameters (e.g. a security key, a multicast connection identifier, etc) can be established differently according to regions and MBS data can be broadcasted within a limited region. Accordingly, when the MSS receiving the MBS data performs handover, the MSS must check whether the MBS information stored in the MSS is valid and the MSS can receive the MBS contents continuously. If a target BS transmits the MBS using parameters different from the information stored in the MSS or does not provide the MBS, the MSS must update parameters for the MBS or access a new BS. To solve such problems the broadband wireless access system adopted the concept of MBS zone within which at least one BS is grouped.
Base stations in an MBS zone transmit the MBS data using identical MBS parameters to MSSs and provide the MSSs with an MBS zone identifier (ID) so that the MSSs recognize the MBS zone. An MSS can check whether the stored MBS information is valid with the MBS zone ID instantaneously. When the MSS moves from a BS into another BS belonging to the same MBS zone, processes for re-establishing MBS related parameters for receiving the MBS are unnecessary. Further, since BSs in the same MBS zone transmit the MBS data using the same radio resources at the same time efficiency of the MBS data reception in the MSSs can be improved with the effect of macro diversity.
Actions for minimizing power consumption in an MSS receiving MBS data are described in detail as follows.
An MSS can diminish power loss during receiving the MBS data notwithstanding a current mode (e.g. a normal mode, sleep mode, or idle mode). A downlink MAP information element (DL-MAP IE) included in a downlink MAP (DL-MAP) message is defined as to indicate bursts transmitted in a current frame. The MSS has to, however, receive and interpret the DL-MAP message in every frame for receiving broadcasted bursts, by which the power loss cannot be diminished. The PS informs the MSS of accurate frames within which the MBS data for the MSS is included so that the MSS does not have to interpret other frames within which the MBS data for the MSS is not included, thereby the power loss can be minimized. Especially, the MBS_MAP IE is more efficient for MSSs in a sleep mode or idle mode. Such scheduling information for the MBS data bursts can be transmitted through an MBS_MAP IE which is one of DL-MAP IEs or in a form of an MAC management message like an MBS MAP message. Table 14 and Table 15 are examples of the MBS_MAP IE and the MBS MAP message, respectively.
TABLE 14SizeSyntax(bits)NotesMBS_MAP_IE{ Extended DIUC4MBS_MAP = 0x05 Length4 Multicast CID1212 LSB of CID for multicast MBS     Zone7MBS Zone identifier corresponds to theidentifieridentifier provided by the BS atconnection initiation Macro  diversity10 = Non Macro-Diversity enhanced zone,enhanced1 = Macro-Diversity enhanced zone If(Macrodiversity enhanced=1) {  Permutation20b00 = PUSC permutation,0b01 = FUSC permutation,0b10 = Optional FUSC permutation,0b11 = Adjacent subcarrier permutation  Idcell6  OFDMA  Symbol8OFDMA symbol offset with respect to startOffsetof the MBS portion  Boosting3It is used to indicate whether boostingis used or not for MBS_MAP message000: normal (not boosted; 001: +6 dB; 010:−6 dB; 011: +9 dB; 100: +3 dB; 101: −3 dB;110: 09 dB; 111: −12 dB  DIUC4DIUC for MBS_MAP message in MBS portion  NO. Subchannels6It is indicate the size of MBS_MAP messagein MBS portion  NO. OFDMA symbols2It is indicate the size of MBS_MAP messagein MBS portion }else{  DIUC4  OFDMA  Symbol8The offset of the OFDMA symbol in whichOffsetthe burst starts, measured in OFDMAsymbols from beginning of the downlinkframe in which the DL-MAP is transmitted.  Subchannel6The lowest index OFDMA subchannel usedoffsetfor carrying the burst, starting fromsubchannel 0.  Boosting3000: normal(not boosted);001: +6 dB; 011: +9 dB010: −6 dB;100: +3 dB; 101: −3 dB;110: −9 dB; 111: −12 dB;  NO. OFDMA Symbols7  NO. Subchannels6  Repetition20b00—No repetition codingCoding Indication0b01—Repetition coding of 2 used0b10—Repetition coding of 4 used0b11—Repetition coding of 6 used  Mext MBS Frame8The Next MBS frame offset value is loweroffset8 bits of the frame number in which theBS shall transmit the next BS frame.  Next MBS OFDMA8The offset of the OFDMA symbol in whichSymbol offsetthe next MBs portion starts, measured inOFDMA symbols from the beginning of thedownlink frame in which the MBS-MAP istransmitted. } if!(byte boundary){  Padding NibblevariablePadding to reach byte boundary }}
TABLE 15SizeSyntax(bits)NotesMBS-MAP    MessageFormat( ){ Management Message Type = ?4Frame number4The frame number is identical to the framenumber in the DL-MAP MBS_DIUC_Change_Count8 #MBS_DATA_IE4Number of included MBS_DATA_IE For(i = 0; i<n; i++){12N = #MBS_DATA_IE  MBS_DATA_IEvariable }8#MBS_DATA_Time_Diversity_IE4Number of includedMBS_DATA_Time_Diversity_IE For(i = 0; i<m; i++){M = #MBS_DATA_Time diversity IEMBS_DATA_Time_Diversity_IEvariable } TLV encoding element If(!byte boundary){  Padding_Nibble }8
Table 16 is an example of an MBS_DATA IE included in the MBS MAP message.
TABLE 16SizeSyntax(bits)NotesMBS_DATA_IE{ MBS_MAP Type = 04 Multicast CID1212 LSB of CID for multicast MBS_DIUC4 OFDMA Symbol offset8OFDMA symbol offset withrespect to start of the MBSportion Subchannel offset6 Boosting3000: normal (not boosted);001: +6 dB; 011: +9 dB010: −6 dB;100: +3 dB; 101: −3 dB;110: −9 dB; 111: −12 dB; NO. OFDMA Symbols7 NO. Subchannels6 Repetition  Coding20b00—No repetition codingIndication0b01—Repetition coding of 2use0b10—Repetition coding of 4used0b11—Repetition coding of 6used Next MBS frame offset8The Next MBS frame offset valueis lower 8bitgs of the framenumber in which the BS shalltransmit the next MBS frame Next MBS OFDMA8The offset of the OFDMA symbolSymbol offsetin which the next MBS portionstarts, measured in OFDMAsymbols from the beginning ofthe downlink frame in which theMBS-MAP is transmitted.}{
During a procedure of generating a service flow for data transmission is performed in a broadband wireless access system, an MSS and a BS establish a connection for the service flow, negotiate service quality parameters, negotiate whether to apply an ARQ protocol to the connection. When the ARQ protocol is applied, parameters for the ARQ protocol are delivered.
Retransmission for an MBS connection, however, is not permitted in the broadband wireless access system in accordance with the conventional art. Accordingly, although an MSS cannot receive some MBS data or receives MBS data having errors due to deterioration of channel circumstances, there has been no way to correct the problems. Further, as described above, the ARQ protocol is defined only for a unicast connection between a BS and an MSS in the conventional system, since reception probability at the time of retransmission can be increased by re-configuring burst profiles (e.g. FEC coding type, modulation type) appropriately according to the channel circumstances based on quality of upload and download signals between a BS and an MSS.
In the case of an MBS, however, since the MBS data is not unicasted by the BS to a specific MSS, but broadcasted to at least one MSS, it is difficult to provide all MSSs receiving the MBS data with appropriate burst profiles and to transmit the MBS data with the most robust burst profiles using radio resources efficiently.
Namely, the conventional art has a problem that the burst profile for transmitting the MBS data cannot be configured appropriately according to the channel circumstances since feedback for the MBS connection has not been defined. Accordingly, it is possible that an MSS cannot receive the MBS data, if the MSS has bad channel circumstances.
Meanwhile, in the conventional ARQ protocol feedback information is transmitted through an ARQ feedback MAC management message from an MSS to a BS. Alternatively, the feedback information is piggybacked in uplink data having no relation with the retransmission, which the MSS transmits to the BS with a different connection ID. In this case, the MSS can transmit the feedback information to the BS only after the MSS requests uplink band for data transmission and then is allocated the uplink band from the BS. Accordingly, specific procedures for the uplink band request, the uplink band allocation, and transmission of feedback information through the allocated uplink band are needed.